Messelite

{{Infobox mineral | name = Messelite | category = Phosphate mineral | boxwidth = | boxbgcolor = | image = Messelite-546647.jpg | imagesize = | caption = Messelite from Germany | formula = Ca2(Fe2+,Mn2+)(PO4)2·2H2O | IMAsymbol = Msl<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref> | molweight = | strunz = 8.CG.05 | dana = 40.2.2.2 | system = Triclinic | class = Pinacoidal ({{overbar|1}}) (same H-M symbol) | symmetry = ''P''{{overbar|1}}<ref name=handbook/> | unit cell = a = 5.8 Å, b = 6.6 Å, c = 5.5 Å α = 102°, β = 109°, γ = 90°; Z = 1 | color = White, pale greenish white, greenish gray, pink,<ref name=handbook/> colorless<ref name=webmin/> | habit = | twinning = | cleavage = Perfect on {001}, producing curved irregular surfaces<ref name=handbook/> | fracture = Uneven<ref name=webmin>{{cite web|title=Messelite |url=http://webmineral.com/data/Messelite.shtml |publisher=Webmineral |access-date=August 7, 2012}}</ref> | tenacity = | mohs = 3.5 | luster = | polish = | refractive = nα = 1.644 nβ = 1.653 nγ = 1.680 | opticalprop = Biaxial (+) | birefringence = δ = 0.036 | 2V = 20° to 35° (measured) | dispersion = Relatively strong | pleochroism = | fluorescence= | absorption = | streak = | gravity = 3.16<ref name=handbook/> | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Translucent<ref name=handbook>{{cite encyclopedia |url=http://www.handbookofmineralogy.com/pdfs/messelite.pdf |title=Messelite |encyclopedia=Handbook of Mineralogy |editor1-first=John W. |editor1-last=Anthony |editor2-first=Richard A. |editor2-last=Bideaux |editor3-first=Kenneth W. |editor3-last=Bladh |editor4-first=Monte C. |editor4-last=Nichols |publisher=Mineralogical Society of America |location=Chantilly, VA |access-date=2012-08-07 |archive-date=2021-07-19 |archive-url=https://web.archive.org/web/20210719165054/http://www.handbookofmineralogy.com/pdfs/messelite.pdf |url-status=dead }}</ref> | other = | references =<ref name=mindat>{{cite web|title=Messelite|url=http://www.mindat.org/min-2658.html|publisher=Mindat|access-date=August 7, 2012}}</ref> }} '''Messelite''' is a mineral with formula Ca2(Fe2+,Mn2+)(PO4)2·2H2O. It was discovered in Germany and described in 1890. The mineral was subsequently discredited in 1940, reinstated and named ''neomesselite'' in 1955, and the name restored to ''messelite'' in 1959.

==Description== Messelite is a translucent mineral that is white, pale greenish white, greenish gray, pink, or colorless.<ref name=handbook/><ref name=webmin/> The mineral may be granular or occur as internally radial aggregates of lamellar crystals arranged as globes, hemispheres, or sheafs, up to {{convert|1.5|cm|in|abbr=on}}.<ref name=handbook/>

Messelite is a member of the fairfieldite group.<ref name=handbook/>

==History== Messelite was discovered in Messel, Hesse, Germany, by a Dr. Spiegel who worked as technical director at a local factory.<ref name=Muthmann93/> The specimen contained a number of crystals associated with carbonaceous material.<ref name=Wolfe790/> It did not conform to any known mineral at the time, a fact confirmed when it was studied at a local mineralogical institute. The mineral was described by W. Muthmann in 1890 in the journal ''Zeitschrift für Kristallographie''<ref name=Muthmann93>{{harvnb|Muthmann|1890|p=93}}</ref> and its formula was identified as (Ca2+,Fe2+,Mn2+)3(PO4)2·{{frac|2|1|2}}H2O.<ref name=Muthmann94/> At the request of Dr. Spiegel, the mineral was named ''messelite'' ({{langx|de|Messelit}}) after the area in which it was discovered.<ref name=handbook/><ref name=Muthmann94>{{harvnb|Muthmann|1890|p=94}}</ref>

The first reevaluation of messelite was carried out by C. W. Wolfe in 1940.<ref name=Wolfe790>{{harvnb|Wolfe|1940|p=790}}</ref> Wolfe concluded that the material was anapaite partially altered to collinsite and he discredited messelite as a valid mineral species.<ref name=Wolfe792>{{harvnb|Wolfe|1940|p=792}}</ref><ref name=Frondel828>{{harvnb|Frondel|1955|p=828}}</ref>

Later, an unaltered mineral was found with the formula (Ca2+,Fe2+,Mn2+)3(PO4)2·2H2O, essentially identical to the formula of messelite reported by Muthmann. It was analyzed by Clifford Frondel and found to be the disordered iron-rich analogue of fairfieldite. Frondel proposed in 1955 that the mineral be named ''neomesselite''.<ref name=Frondel828/>

A few years later, additional material was obtained from the type locality of Messel and studied with optical and x-ray methods. The specimen was determined to consist primarily of material identical to the neomesselite described by Frondel with a rim of anapaite. Since it is likely that the mixture studied by Muthmann was primarily this mineral, it was decided around 1959 that the name ''neomesselite'' should be discarded in favor of ''messelite''.<ref name=Fleischer>{{cite journal|last=Fleischer|first=Michael|title=New Data: Messelite, Neomesselite|journal=American Mineralogist|date=March–April 1959|volume=44|issue=3 & 4|url=http://www.minsocam.org/ammin/AM44/AM44_464.pdf|page=469|publisher=Mineralogical Society of America}}</ref> When the IMA was founded, messelite was grandfathered as a valid mineral species.<ref name=mindat/>

==Occurrence== Messelite has been found in Austria, Brazil, Canada, Czech Republic, France, Germany, Japan, Kazakhstan, Spain, Sweden, Switzerland, Ukraine, and the United States.<ref name=handbook/><ref name=mindat/>

The mineral tends to form in granite pegmatites by hydrothermal alteration at a late stage. Messelite occurs in association with amblygonite, anapaite, brazilianite, eosphorite, fairfieldite, goyazite, graftonite, herderite, hureaulite, ludlamite, phosphoferrite, siderite, triphylite, vivianite, and whitlockite.<ref name=handbook/>

==References== {{Reflist|30em}}

;Bibliography *{{cite journal|last=Frondel|first=Clifford|title=Neomesselite and beta-roselite: two new members of the fairfieldite group|journal=American Mineralogist|date=September–October 1955|volume=40|issue=9 & 10|pages=828–833|url=http://www.minsocam.org/ammin/AM40/AM40_828.pdf}} *{{cite journal|last=Muthmann|first=W.|title=Kürzere Originalmittheilungen und Notizen: Messlit, ein neues Mineral|journal=Zeitschrift für Kristallographie, Kristallgeometrie, Kristallphysik, Kristallchemie|date=1890|volume=17|pages=93–94|url=https://books.google.com/books?id=rlQPAAAAIAAJ&pg=PA93|publisher=Akademische Verlagsgesellschaft|language=de}} *{{cite journal|last=Wolfe|first=C. W.|title=Classification of minerals of the type A3(XO4)2·''n''H2O (concluded)|journal=American Mineralogist|date=December 1940|volume=25|issue=12|pages=787–809|url=http://www.minsocam.org/ammin/AM25/AM25_787.pdf}}

==External links== {{commonscat-inline|Messelite|lcfirst=yes}}

Category:Triclinic minerals Category:Calcium minerals Category:Iron(II) minerals Category:Manganese(II) minerals Category:Phosphate minerals Category:Dihydrate minerals Category:Minerals in space group 2